If the Mars Climate Orbiter resists all attempts to rescue it - and that seems almost certain now - then many scientists and engineers will have to face its loss with stoic resignation. The Red Planet will have claimed another victim.

Over the years, Mars has collected many trophies. Some spacecraft have failed to even leave the Earth, some have failed in interplanetary flight, some have flown past Mars and others have reached the surface only to send back a signal of static and then die.

But those that have succeeded have shown us a world of wonders. Beneath its peach-coloured sky, Mars has craters and canyons, wind and cloud, shifting sand dunes and morning mist, mountain ranges, canyons that dwarf anything we have on Earth and extinct volcanoes that are sometimes buried up to their necks in cloud.

The last victim was the sophisticated and expensive Mars Observer, that failed to enter orbit in 1993. It is now orbiting the Sun somewhere in deep space.

Major successes

Following that disaster, it was decided that future missions would not be so complex so that if another spacecraft was lost it would not be such a body blow. Hence the Mars Global Surveyor (MGS) and the Mars Climate Orbiter (MCO) were born.

MGS is currently in orbit around Mars and is sending back superb images of the surface. MCO was due to do the same for the atmosphere. But even if MCO is lost forever, overall, scientists have done remarkably well in sending unmanned spacecraft to explore the planets. Far more often than not, these missions have exceeded expectations.

Perhaps it is the successes that have given space engineers a overly optimistic assessment of the risk of failure. But failure is a part of space exploration and it will never go away.

The environment of space is a harsh and unforgiving one. If, as we suspect, MCO is lost for good a big question mark will hang over the next Mars mission. This is the Mars Polar Lander. It was launched in January and is due to touch down in December.

MCO was due to act as a relay station for the lander. I expect that already, even before all hope is lost of recovering the Mars Climate Orbiter, backup plans are being consulted.